1. Field of the Invention
The present invention relates to a video microscope, and more particularly to an improvement of a video microscope which allows a magnification for forming an image of an object to be variably and automatically set with the touch of a button in a wide range without changing the lens, etc. and which allows itself to automatically focus on the object simultaneously therewith.
2. Description of the Related Art
In a conventional video microscope of this type, it is common that the lens system itself is fixed with respect to an object; i.e., it is of a fixed focused type. Thus, in order to change an enlarging (or reducing) magnification for the formed image of the object, the lens system must be changed, and this requires that a set of lens systems corresponding to magnifying requirements should be prepared.
Further, a zoom lens system can be employed as a means for changing the enlarging (or reducing) magnification for the formed image of the object. With this system, however, the magnification can be varied only in such a relatively narrow range as, usually, within several times, and thus it is difficult to obtain a wide range of magnifications with this system.
On the other hand, Japanese Patent No. 2509120 has proposed a solution. That is, in the proposed system, the position of a lens body tube incorporating a lens system therein is adjusted by sliding the lens body tube using an objective distance adjusting mechanism, so that the objective distance of an object relative to the object side of the lens system can be adjusted. Further, the position of a video signal converting section tube having a two-dimensional CCD element is adjusted relative to the lens body tube by sliding the video signal converting section tube based on the enlarging (or reducing) magnification and using a focus adjusting mechanism. As a result of these adjustments, this system allows predetermined enlarging (or reducing) magnifications to be provided for the object in a wide range without changing the lens.
However, the proposed system involves, without fail, focus adjustment every time a predetermined enlarging (or reducing) magnification is set, and thus two-step operations are required. In addition, if the object is largely out of focus, it is difficult to find a direction for the adjustment, and thus these operations entail a lot of time and labor.
The present invention has been made to overcome these conventional problems. An object of the invention is, therefore, to provide a video microscope of this type which allows a magnification for forming an image of an object to be variably and automatically set in a wide range with the touch of a button while driving motors without changing the lens, etc. and which also allows itself to automatically focus on the object simultaneously therewith by driving the motors.
To achieve the above object, according to one aspect of the present invention, there is provided a video microscope, which comprises: an observation stand whose position is fixed relative to an object; a lens body tube having a lens system arranged at one end thereof along an imaging optical path with respect to the object and being inserted into the observation stand so as to be movable in the optical axis direction; a video signal converting section tube having an image pickup element arranged at a predetermined position corresponding to the lens system, being arranged so as to be movable in the optical axis direction relative to the observation stand, and being arranged so as to be movable relative to the lens body tube; an objective distance adjustment drive motor for moving the lens body tube in the optical axis direction by driving an objective distance adjusting mechanism and an objective distance position detecting sensor which are arranged between the observation stand and the lens body tube, the objective distance adjusting mechanism serving to adjust an objective distance between the object and a principal point on the object side of the lens system, the objective distance position detecting sensor serving to detect the objective distance; an object imaging distance adjustment drive motor for moving the video signal converting section tube in the optical axis direction by driving an object imaging distance adjusting mechanism and an object imaging distance position detecting sensor which are provided between the observation stand and the video signal converting section tube, the object imaging distance adjusting mechanism serving to adjust an object imaging distance between the object and the image pickup surface of the image pickup element, the object imaging distance position detecting sensor serving to detect the object imaging distance; and an arithmetic controller for setting the objective distance and the object imaging distance to predetermined positions by driving the objective distance adjustment drive motor and the object imaging distance adjustment drive motor. In such a video microscope, in response to a position detection signal from the objective distance position detecting sensor and a position detection signal from the object imaging distance position detecting sensor, the arithmetic controller can automatically adjust and set the positions of the lens body tube and the video signal converting section tube by respectively driving the objective distance adjustment drive motor and the object imaging distance adjustment drive motor in such a manner that the object can be in focus on the image pickup element at a set magnification.
According to another aspect of the present invention, in addition to the aforementioned video microscope, the image pickup element is constructed of a two-dimensional CCD element and an illuminating light for illuminating the object is provided at the distal end of one of the lens body tube and the observation stand.
Further, according to still another aspect of the present invention, in addition to the aforementioned video microscope, a video magnification setting unit that sets a magnification for magnifying an image obtained by the image pickup element is provided, and the arithmetic controller drives both motors so that the objective distance and the object imaging distance are adjusted to such predetermined positions as to correspond to a video magnification based on a video magnification setting signal from the video magnification setting unit.
Further, according to still another aspect of the present invention, in addition to the aforementioned video microscopes, both motors are longitudinally arranged in such a manner that output shafts thereof project in the optical axis direction. As a result of this arrangement, both motors are compactly accommodated in the observation stand and thus the whole video microscope can be made compact.
Further, according to still another aspect of the present invention, in addition to the aforementioned video microscopes, the set magnification can be changed to a desired magnification with the object being in focus on the image pickup element by moving the lens body tube and the video signal converting section tube in such a manner that the objective distance value and the object imaging distance value always correspond to any magnifications obtained in the course of changing the set magnification to the desired magnification. As a result of this arrangement, the object is kept in focus at all times while the magnification is being changed, and thus the user can have an improved visibility, e.g., when the user wishes to enlarge a specific portion of the object.
Further, according to still another aspect of the present invention, in addition to the aforementioned video microscopes, the observation stand, each of the lens body tube and the video signal converting section tube is formed into a tube having a rectangular cross section, and the objective distance adjustment drive motor and the object imaging distance adjustment drive motor are arranged both between the observation stand and the lens body tube and on one side surface or between two side surfaces. As a result of this arrangement, the space within the observation stand can be utilized effectively, and thus the video microscope can be made compact.
Further, according to still another aspect of the present invention, in addition to the aforementioned video microscopes, both motors are arranged on the back surface of the observation stand. As a result of this arrangement, the width in the horizontal direction of the video microscope can be made narrow. Still further, according to still another aspect of the present invention, in addition to the aforementioned video microscopes, both motors are vertically overlapped one upon another in the optical axis direction. As a result of this arrangement, the space can be utilized effectively, and thus the whole video microscope can be downsized.
Further, according to still another aspect of the present invention, there is provided a video microscope, in which an objective distance between an object and a principal point on the object side of a lens system can be adjusted by a motor for driving both a mechanism and a position sensor for detecting the position of the mechanism integrally, the mechanism serving to adjust a lens body tube relative to an observation stand in such a manner that the lens body tube internally slides along the observation stand, the lens body tube incorporating the lens system therein and having an illuminating light for illuminating the object arranged therein, the observation stand confronting the object, and in which an object imaging distance between the object and a two-dimensional CCD element can be adjusted by a motor for driving a mechanism and a position sensor for detecting the position of the mechanism integrally, the mechanism serving to adjust a video signal converting section tube relative to the observation stand so that the video signal converting section tube internally slides along the observation stand, the video signal converting section tube having the two-dimensional CCD sensor internally sliding along the lens body tube. In such a video microscope, by using a video magnification setting unit and an arithmetic controller which are prepared separately from the video microscope, the objective distance and the object imaging distance corresponding to a video magnification set when the object has been in focus are automatically adjusted and set to an objective distance (a) and an object imaging distance (L) corresponding to the set video magnification by calculating and controlling an objective distance adjustment drive motor and an object imaging distance adjustment drive motor so that the lens body tube and the video signal converting section tube are moved to such positions as to always satisfy predetermined relational expressions.
The aforementioned predetermined expressions are the following expressions (1) to (3).
1/a+1/b=1/fxe2x80x83xe2x80x83(1)
(basic formula)
a=f+f/mxe2x80x83xe2x80x83(2)
L=f(2+1/m+m)+txe2x80x83xe2x80x83(3)
f: Focal length of the lens system
a: Objective distance (distance from the object to the principal point on the object side of the lens system)
b: Imaging distance (distance from the principal point on the imaging side of the lens system to the two-dimensional CCD surface)
m=b/a: Imaging magnification of the lens system (dimension of the formed image/dimension of the object)
L=a+b+t: Object imaging distance (distance from the object to the two-dimensional CCD surface)
t: Lens thickness (distance from the principal point on the object side to the principal point on the imaging side of the lens system)
That is, the video microscope is constructed so that the expressions (2) and (3) are derived from the basic formula for a convex lens: 1/a+1/b=1/f, and the objective distance adjustment drive motor and the object imaging distance adjustment drive motor are controlled to be driven by the arithmetic controller in such a manner that the objective distance and the object imaging distance are automatically adjusted and set to the objective distance (a) and the object imaging distance (L) corresponding to the set imaging magnification.
Therefore, according to the aforementioned aspects of the present invention, the objective distance is controlled by the objective distance adjustment drive motor, and the object imaging distance is controlled by the object imaging distance adjustment drive motor, and such controls are effected by the arithmetic controller, which controls the motors based on its calculation made in response to a predetermined magnification setting signal as well as position detection signals from the objective distance position detecting sensor and the object imaging distance position detecting sensor. That is, the arithmetic controller automatically adjusts and sets the respective motors so that the lens body tube and the video signal converting section tube are moved to such positions as to set a predetermined magnification and allow the object to be in focus at the same time. As a result, a clear image of the object can be formed while projected on the image pickup element at an arbitrarily set enlarging (or reducing) magnification. Thus, the video microscope according to the present invention does not require lens systems to be changed nor does it involve laborious focusing and related operations when the magnification is varied manually.
Further, according to still another aspect of the present invention, in addition to the aforementioned video microscopes, both motors are longitudinally arranged in such a manner that output shafts thereof project in the optical axis direction. As a result of this arrangement, both motors are compactly accommodated in the observation stand, and thus the whole video microscope can be made compact.
Further, according to still another aspect of the present invention, in addition to the aforementioned video microscopes, the set magnification can be changed to a desired magnification with the object being in focus on the image pickup element by moving the lens body tube and the video signal converting section tube in such a manner that the objective distance value and the object imaging distance value always correspond to any intermediate magnifications obtained in the course of changing the set magnification to the desired magnification. As a result of this arrangement, the object is kept in focus at all times while the magnification is being changed, and thus the user can have an improved visibility, e.g., when the user wishes to enlarge a specific portion of the object.
Further, according to still another aspect of the present invention, in addition to the aforementioned video microscopes, the observation stand, each of the lens body tube and the video signal converting section tube is formed into a tube having a rectangular cross section, and the objective distance adjustment drive motor and the object imaging distance adjustment drive motor are arranged both between the observation stand and the lens body tube and on one side surface or between two side surfaces. As a result of this arrangement, the space within the observation stand can be utilized effectively, and thus the video microscope can be made compact.
Further, according to still another aspect of the present invention, in addition to the aforementioned video microscopes, both motors are arranged on the back surface of the observation stand. As a result of this arrangement, the width in the horizontal direction of the video microscope can be made narrow. Still further, according to still another aspect of the present invention, in addition to the aforementioned video microscopes, both motors are vertically overlapped one upon another in the optical axis direction. As a result of this arrangement, the space can be utilized effectively, and thus the whole video microscope can be downsized.